JP2008521659A - Printhead and system using printhead - Google Patents

Abstract

  In general, in one aspect, the present invention provides an apparatus that includes an injection assembly that includes a plurality of nozzles capable of ejecting droplets, and a first reservoir and a second reservoir. Characteristically, the first and second reservoirs communicate with the injection assembly and with each other.

Description

Related patent applications

  In accordance with 35 USC 119 (e) (1), this application is a "printhead and filed" filed December 3, 2004, the entire contents of which are incorporated herein by reference. No. 60 / 632,803, entitled “System Using Printhead”.

  The present invention relates to a print head and a system using the print head.

  Ink jet printers generally include an ink path from an ink supply to a nozzle path. The nozzle passage terminates in a nozzle hole from which ink droplets are ejected. Ink droplet ejection is controlled by pressurizing ink in the ink path using an actuator such as a piezoelectric deflector, a thermal bubble jet generator, or an electrostatically deflected element. The A typical printhead includes one reservoir and one ejection assembly. The ejection assembly includes an array of ink passages with corresponding nozzle holes and cooperating actuators so that the ejection of ink droplets from each nozzle hole can be independently controlled. In a drop-on-demand (pressure-controlled) print head, each actuator is actuated while the ejection assembly and the printing medium move relative to each other, and a specific pixel position in the image The ink droplets are selectively ejected at. In a high-performance injection assembly, nozzle holes having a diameter of 50 μm or less, for example, a diameter of about 25 μm, are arranged at intervals of 40 to 120 nozzles / cm (100 to 300 nozzles / inch), and 100 to 300 dpi or more. And having a resolution of about 1 to 70 picoliters or less. The droplet ejection frequency is 10 kHz.

  In US Pat. No. 6,057,028, the entire contents of which are incorporated herein by reference, an injection assembly including a semiconductor body and a piezoelectric actuator is described. The body of the assembly is formed from silicon that has been etched to define a plurality of ink chambers. The nozzle holes are defined in an independent nozzle plate attached to the silicon body. Piezoelectric actuators include a layer of piezoelectric material that changes shape or bends in response to an applied voltage. When the piezoelectric material layer is bent, the ink in the pumping chamber disposed along the ink passage is pressurized.

  A further example of an injection assembly can be found in U.S. patent application filed July 3, 2002 entitled "Printhead", the entire contents of which are incorporated herein by reference. It is disclosed.

  The amount of bending of the piezoelectric material proportional to the applied voltage is inversely proportional to the thickness of the piezoelectric material. As a result, the required voltage increases as the thickness of the piezoelectric material layer increases. In order to limit the voltage required for a given ink droplet size, the area of the flexure wall of the piezoelectric material may be increased. As the area of the piezoelectric material deflection wall increases, a correspondingly large pumping chamber is also required, which can complicate design aspects such as maintaining narrow orifice spacing for high resolution printing.

In general, a printhead can include one or more injection assemblies. The printing system can print by one or more relative passes of the substrate to the print head. The print head can be used, for example, to eject ink and / or other fluids such as those used in electronic components for panel displays (eg, conductive materials) or color filters.
US Pat. No. 5,265,315 US patent application Ser. No. 10 / 189,947

  Unintentional pressure changes inside the injection assembly can lead to undesirable effects. For example, an increase in pressure undesirably ejects fluid from a jet in the injection assembly. In contrast, a drop in pressure results in incomplete filling of the fluid in the jet in the injection assembly. In other words, the drop in pressure can lead to incomplete fluid filling of the jet nozzle, leading to air entrapment that affects the jet's ability to eject droplets of fluid.

  The acceleration of the print head causes a pressure change inside the firing assembly. The magnitude of such pressure fluctuations increases with increasing distance between the reservoir in the printhead and the ejection assembly. In general, for a constant acceleration, pressure fluctuations increase as the distance between the reservoir and the injection assembly increases. Thus, in a printhead where the firing assembly is located relatively far from the reservoir, even the acceleration associated with the relatively modest movement of the printhead can lead to undesirable firing and / or print loss. is there. For example, if the reservoir supplies fluid to a collection of injection assemblies, fluid incomplete filling may occur in some or all of the injection assemblies when the injection assembly is moved for cleaning or other maintenance There is.

  The print head can include a sudden pressure change suppression mechanism to reduce the amount of fluid pressure change in the ejection assembly as the print head moves. The sudden pressure change suppressing mechanism has, for example, a second reservoir chamber communicating with the first reservoir chamber and the injection assembly, or a followability that allows a change in the volume of fluid in the manifold that supplies fluid from the reservoir chamber to the injection assembly. be able to.

  In general, in one aspect, the invention features a system that includes a printhead assembly configured to deposit droplets of an ejected fluid on a substrate, and the printhead assembly. A mounting frame for mounting to the substrate, and the print head assembly includes a plurality of ejection assemblies and a pair of storage chambers configured to supply ejection fluid to the plurality of ejection assemblies. It is characterized by being.

  Embodiments of this system can include one or more of the following features and / or features of other aspects. For example, the system can further comprise an electronic controller configured to maintain the volume of ejected fluid in the reservoir within about 95% of the maximum volume. The system may further include a first fluid conduit that connects the pair of reservoirs and provides a passage for the ejected fluid between the pair of reservoirs. The system may further comprise a plurality of additional fluid conduits that provide a passage for the ejected fluid from the first fluid conduit to the plurality of ejector assemblies. The plurality of additional fluid conduits may have a narrower inner diameter than the first fluid conduit. The system can include a second fluid conduit that is different from the first fluid conduit, the second fluid conduit being for an injection fluid from the plurality of reservoirs to the plurality of injection assemblies. Provide a passage. The mounting frame may comprise an assembly that allows the print head assembly to be moved from an ejection position relative to the substrate to a second position away from the substrate.

  In another aspect, the invention features an apparatus that includes an injection assembly that includes a plurality of nozzles capable of ejecting droplets, a first reservoir, and a second reservoir. These first and second storage chambers communicate with the injection assembly and with each other.

Embodiments of this device can include one or more of the following features and / or features of other aspects. For example, the injection assembly can be positioned about 10 cm or more away from the first reservoir. The injection assembly can be positioned about 10 cm or more away from the second reservoir. The first storage chamber can be arranged at a distance of about 10 cm or more from the second storage chamber. The first and second storage chambers can reduce the pressure change of the fluid in the injection assembly that is generated by the acceleration of the apparatus. The apparatus is about 10 ms ^-2 or less (e.g., about ^{9 ms -2} or less, about ^{8 ms -2} or less, about ^{7 ms -2} or less, about ^{6 ms -2} or less, about ^{5 ms -2} or less, about ^{4 ms -2} or less, about 3 ms ^{- 2} or less, approximately 2 ms ^-2 or less, or approximately 1 ms ^-2 or less), the pressure change can be sufficiently reduced so that incomplete filling of the fluid in the nozzle does not substantially occur. is there. The device of about 10 ms ^-2 or less (e.g., about ^{9 ms -2} or less, about ^{8 ms -2} or less, about ^{7 ms -2} or less, about ^{6 ms -2} or less, about ^{5 ms -2} or less, about ^{4 ms -2} or less, about 3 ms ^{- 2} or less, approximately 2 ms ^-2 or less, or approximately 1 ms ^-2 or less), the pressure change is sufficiently reduced so that fluid in the inkjet printhead module does not substantially leak from the nozzle. Is possible. The apparatus can include a frame having an opening in which the injection assembly is disposed. The apparatus can further comprise one or more additional injection assemblies disposed in corresponding openings in the frame. The first and second reservoirs are in communication with the additional injection assembly. The frame may be part of an enclosure that houses the injection assembly and the first and second reservoirs.

  The injection assembly can include a body and a nozzle plate. The main body of the injection assembly may include a plurality of flow paths and a single piezoelectric actuator, the plurality of flow paths corresponding to the plurality of nozzles in the nozzle plate, and the piezoelectric actuator serving as the plurality of flow paths. And a fluid droplet is ejected through the plurality of nozzles.

  Embodiments of the invention can have one or more of the following advantages. These embodiments have a print head assembly provided with a pressure sudden change suppression mechanism. This sudden pressure change suppression mechanism can reduce incomplete fluid filling or unnecessary ejection of the ejection assembly within the printhead assembly due to the “water hammer” effect associated with the acceleration of the printhead assembly. . This can reduce system downtime due to fluid incomplete filling of the injection assembly. Also, unnecessary ejection of ink can be reduced. In some embodiments, a dual reservoir system can improve fluid flow and / or reduce depletion for an ejection assembly (eg, an assembly located relatively far from the reservoir).

  The details of one or more embodiments of the invention are set forth below with reference to the drawings. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

  FIG. 1A shows a schematic view of a printing line 10 with a printhead assembly 100. The printhead assembly 100 causes the ejection assembly within the assembly to deposit ink droplets 20 on the substrate 18 as the substrate 18 moves through the printhead assembly (in the x direction). In addition, they are arranged with respect to the printing body 18 made of a continuous sheet-like body. The printing line 10 includes a plurality of rollers 16 that support a printing medium 18 formed of a continuous sheet-like body and move the printing medium through a print head assembly.

  In some embodiments, the print line 10 includes additional printhead assemblies (eg, two or more printhead assemblies, three or more printhead assemblies, four or more printhead assemblies). I have.

  A control module 12 and a supply tank 14 are attached to the print head assembly 100. The control module 12 includes control electronics and a user interface that allows an operator to start, stop, and adjust the operation of the printhead assembly 100. The control module 12 also includes an electronic circuit that controls the ejection timing of the droplets from the ejection assembly and synchronizes the ejection to the position of the moving substrate.

  The control module 12 communicates with the supply tank 14 and cooperates with the ink in the supply tank 14 to fill the storage chamber in the print head assembly 100. Electronic components in the control module 12 receive signals from ink level sensors in the printhead assembly 100 that indicate when additional ink is needed in the printhead assembly reservoir. Upon receiving these signals, the control module 12 sends a signal to the supply tank 14, operates a pump provided in the supply tank, and sends a certain amount of ink from the supply tank to the print head assembly 100. Each reservoir in the printhead assembly 100 includes an ink level sensor, but in some embodiments, only a single reservoir has an ink level sensor. The control module can supply ink to both storage chambers based on a signal from the ink level sensor.

  Referring to FIG. 1B, the print head assembly 100 is attached to a mounting frame 22, and the mounting frame 22 suspends the print head assembly over a substrate 18 that is a continuous sheet-like body. . The fixture of the mounting frame 22 includes a sliding bracket 24 that slides the printhead assembly onto the substrate without the operator having to remove the printhead assembly from the mounting frame 22. It can be moved laterally (in the Y-axis direction) from the position 25 to a position away from the printing medium shown in FIG. At a position away from the substrate, the operator can access the electronic component more easily than when the print head assembly is at the position 25. This can make maintenance of electronic components easier. When the print head assembly is slid between two positions, acceleration occurs in the print head assembly. As described below, embodiments of the printhead assembly include components that reduce (eg, eliminate) undesirable fluid ejection or ink incomplete filling of the jet resulting from this acceleration.

  Schematically speaking, the properties of a substrate to be printed consisting of continuous sheet-like bodies vary. In some embodiments, the substrate is a paper sheet. In certain embodiments, the sheet can include a polymer (eg, an extruded or molded polymer sheet). In the embodiment, the sheet-like body may be formed from food (for example, bread dough).

  Furthermore, even if the printing body 18 is a continuous sheet-like body, in some embodiments, the printing body may be in a discontinuous form. For example, the system 10 can include a platen that supports individual print body portions and transports them to the print head assembly rather than a print body comprising a continuous sheet-like body. Examples of non-continuous substrates include paper or cardboard sheets, polymer sheets, individual food items (eg cookies), or electronic components.

  Generally speaking, there are various types of ejection fluid. The ejection fluid can be an ink (eg, UV curable ink, heat fusion ink, and / or solvent type ink). In some embodiments, the ejection fluid is a conductive component (eg, solder), an electrical insulator component (eg, a polymer used as a dielectric in a microelectronic device), or an optically active component (eg, A component of an organic light emitting material, or a color filter).

  With reference to FIGS. 2 and 3, the printhead assembly 100 includes a housing 110 that supports six injection assemblies 130, 132, 134, 136, 138 and 140, and two reservoirs 120 and 122. Yes. The storage chambers 120 and 122 communicate with each other through a tube 150 (for example, a rubber tube). Injection assemblies 130, 132, 134, 136, 138 and 140 communicate with reservoirs 120 and 122 through tubes 152, 154, 156, 158, 160 and 162 connected to tube 150, respectively. Fluid is supplied to reservoirs 120 and 122 through supply tubes 172 and 171 from remote fluid sources.

  Reservoir chambers 120 and 122 are provided with deaeration members 165 and 170, respectively. These deaeration members 165 and 170 inject the dissolved air into the tube 150 before the ink flows into the tubes 150 from the respective reservoir chambers. Remove from. In some embodiments, the degassing member comprises a gas permeable membrane (eg, Teflon®) that isolates the fluid from one chamber. The chamber is depressurized to remove dissolved air from the fluid in contact with the membrane.

  The storage chamber 122 also includes a fluid level sensor 230 that detects when the fluid level 240 in the storage chamber drops below a predetermined volume. When the level drops below this volume, sensor 230 sends a signal to a pump (not shown) that sends additional fluid from a remote fluid source to the reservoir. Although not shown in the printhead assembly 100, in some embodiments, a sensor is also provided in the reservoir 120 to detect the fluid level 242.

  Both storage chambers 120 and 122 are connected to a vacuum pump 220 through a decompression line 210. The vacuum pump depressurizes each storage chamber to adjust the atmospheric pressure of the fluid in the print head assembly.

  The fluid levels 240 and 242 are maintained such that there is sufficient additional volume in each reservoir to accommodate changes in fluid volume as the printhead assembly moves. In particular, additional capacity within each reservoir is severe within the injection assemblies 130, 132, 134, 136, 138, and 140, for example when the printhead assembly is moved for cleaning and / or other maintenance. Without causing a significant pressure fluctuation, the “bounce around” of the fluid between the storage chambers is adjusted. In this way, unnecessary fluid ejection and / or incomplete fluid filling of the jet can be avoided.

  In general, the capacity of the reservoirs 120 and 122 can vary. Generally, the reservoir volume is selected based on the number of ejection assemblies in the printhead assembly and the expected throughput of the print line. In some embodiments, the capacity of reservoir 120 and / or 122 is in the range of about 50 milliliters to about 2 liters (eg, about 100 milliliters to about 1 liter, such as about 500 milliliters). Within range).

  In some embodiments, fluid levels 240 and / or 242 are maintained at a level that is at most about 95% of the capacity of reservoirs 120 and 122. For example, the fluid levels 240 and / or 242 can be maintained at 90% or less (eg, about 80% or less, about 70% or less, about 60% or less, about 50% or less) of the capacity of each reservoir.

  In general, the distance between reservoir 120 and 122 and the distance between reservoir and injection assemblies 130, 132, 134, 136, 138 and 140 may vary. In some embodiments, the distance between reservoirs 120 and 122 can be relatively long. For example, if the printhead assembly 100 is configured to print across a wide range of substrates, the distance occupied by the injection assembly is relatively long, resulting in a relatively long distance between reservoirs. Become. In some embodiments, the reservoirs 120 and 122 are about 50 cm or more (e.g., about 60 cm or more, about 70 cm or more, about 80 cm or more, about 90 cm or more, about 100 cm or more, about 110 cm or more, about 120 cm or more, About 130 cm or more, about 140 cm or more, about 150 cm or more).

  In some embodiments, the flow resistance of tubes 152, 154, 156, 158, 160 and 162 can be different from tube 150. In some embodiments, the flow resistance of the tubes 152, 154, 156, 158, 160 and 162 can be higher than the tube 150. For example, if the entire ejection assembly is flexible, the flow resistance of the tubes 152, 154, 156, 158, 160 and 162 relative to the tube 150 will cause pressure fluctuations within the ejection assembly caused by movement of the printhead assembly. The size can be reduced. In some embodiments, tubes 152, 154, 156, 158, 160 and 162 have a smaller inner diameter than tube 150, resulting in increased flow resistance compared to tube 150. For example, the inner diameter of the tubes 152, 154, 156, 158, 160 and 162 is about 75% or less (about 70% or less, about 60% or less, about 50% or less, about 40% or less, about 30) of the inner diameter of the tube 150. % Or less, about 20% or less, or about 10% or less).

  The printhead assembly 100 includes six injection assemblies, but is generally not limited in embodiments. In general, the number of firing assemblies in the printhead assembly can vary. In some embodiments, the printhead assembly can comprise more than 6 (eg, 7 or more, 8 or more, 9 or more, 10 or more) ejection assemblies. Further, in general, the print head assembly can include more than two (eg, 3 or more, 4 or more) storage chambers.

  The dual reservoirs in the printhead assembly 100 include a pair of free fluid surfaces that adjust the bouncing of the fluid, although other configurations can provide this property. For example, referring to FIG. 4, in some embodiments, the printhead assembly 300 includes a single elongated reservoir having two portions 310 and 311 that are each configured to include a free fluid surface. Can be used. These free fluid surfaces are shown as surfaces 301 and 302 for portions 310 and 311 respectively. The elongate reservoir also includes a third portion 312 (eg, a tube) that connects portions 310 and 311. This reservoir is in communication with the injection assemblies 320, 322 and 324 through the tube 350 (which connects the portions 310 and 311) and the tubes 351, 352 and 353.

  Alternatively, in some embodiments, the printhead assembly can comprise a single reservoir having a free surface over most or all of the injection assembly within the assembly.

  Although a number of embodiments of the invention have been described above, it should be understood that various modifications can be made without departing from the spirit and scope of the invention. For example, in the above-described embodiment, the print head includes a substrate that is moved while being held so as not to move, but some embodiments may move relative to a substrate that does not move. Or a system in which both the printhead assembly and the substrate are moved relative to the frame that supports the printhead assembly and the substrate. Accordingly, other embodiments are within the scope of the appended claims.

Schematic of printing line with printhead assembly Plan view of the printing line of FIG. 1A Plan view of print head assembly Schematic diagram of the print head assembly shown in FIG. Schematic diagram of another printhead assembly

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Print line, printing system 12 Control module 14 Supply tank 18 Printed body 22 Mounting frame 16 Mounting rack 100,300 Print head assembly 120,122 Reservoir 130,132,134,136,138,140 Injection assembly 150,152 , 154, 156, 158, 160, 162 tubes

Claims (20)

A printhead assembly configured to deposit droplets of ejected fluid on the substrate; and a mounting frame for attaching the printhead assembly to the substrate.
The printhead assembly includes a plurality of ejection assemblies and a pair of reservoirs configured to supply ejection fluid to the plurality of ejection assemblies.   The system of claim 1, further comprising an electronic controller configured to maintain a volume of the ejected fluid in the storage chamber below about 95% of a maximum volume of the storage chamber. .   The system of claim 1, further comprising a first fluid conduit connecting the pair of reservoirs to provide a passage for the ejected fluid between the pair of reservoirs.   The system of claim 3, further comprising a plurality of additional fluid conduits that provide passages for the ejected fluid from the first fluid conduit to the plurality of ejector assemblies.   The system of claim 4, wherein the plurality of additional fluid conduits have a narrower inner diameter than the first fluid conduit.   A second fluid conduit different from the first fluid conduit, the second fluid conduit providing a passage for the ejected fluid from the plurality of reservoirs to the plurality of ejection assemblies; The system of claim 3.   The mounting frame includes an assembly that allows the print head assembly to be moved from an ejection position with respect to the printing body to a second position away from the printing body. Item 1. The system according to Item 1. An injection assembly with a plurality of nozzles capable of discharging droplets;
An apparatus comprising: a first storage chamber and a second storage chamber, the first and second storage chambers communicating with the injection assembly and communicating with each other.   The apparatus of claim 8, wherein the injection assembly is positioned about 10 cm or more away from the first reservoir.   The apparatus of claim 9, wherein the injection assembly is positioned about 10 cm or more away from the second reservoir.   The apparatus according to claim 8, wherein the first storage chamber is arranged at a distance of about 10 cm or more from the second storage chamber.   9. The apparatus of claim 8, wherein the first and second reservoirs reduce fluid pressure changes in the ejection assembly that are caused by the acceleration of the apparatus. Wherein when the device is accelerated by about 10 ms ^-2 or less, according to claim 12, wherein the fluid underfilled in the nozzle, wherein the pressure changes so as not substantially occur can be sufficiently reduced. The pressure change is sufficiently reduced so that fluid in an inkjet printhead module does not substantially leak from the nozzle when the device is accelerated by about 10 ms ^-2 or less. Item 13. The device according to Item 12.   9. The apparatus of claim 8, wherein the frame includes an opening, and the injection assembly is disposed in the opening.   The apparatus of claim 15, further comprising one or more additional injection assemblies disposed in corresponding openings in the frame.   16. The apparatus of claim 15, wherein the first and second reservoirs are in communication with the additional injection assembly.   The apparatus of claim 16, wherein the frame is part of an enclosure that houses the injection assembly and the first and second reservoirs.   The apparatus of claim 8, wherein the injection assembly comprises a body and a nozzle plate.   The body of the injection assembly includes a plurality of channels and a piezoelectric actuator, the plurality of channels corresponding to a plurality of nozzles in the nozzle plate, and the piezoelectric actuator generates a pressure change in the plurality of channels. 21. The apparatus of claim 19, wherein the apparatus is configured to eject fluid droplets through the plurality of nozzles.

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